CODEWITHSUNDEEP
rdifference
HappyPy
HappyPy

Reputation: 10697

calculate difference between values of a column

dat <- data.frame(s=c(1,1,1,1,2,2,2,2,3,3,3,3),               
                 c1=c("w","x","y","z","w","x","y","z","w","x","y","z"), 
                 c2=c("m","m","m","m","f","f","f","f","m","m","m","m"), 
                 c3=c(1,2,3,4,5,6,7,8,9,10,11,12))

> dat
       s c1 c2 c3
    1  1  w  m  1
    2  1  x  m  2
    3  1  y  m  3
    4  1  z  m  4
    5  2  w  f  5
    6  2  x  f  6
    7  2  y  f  7
    8  2  z  f  8
    9  3  w  m  9
    10 3  x  m 10
    11 3  y  m 11
    12 3  z  m 12

I'd like to calculate the difference between the c3 values for every combination of c1 (w-x, x-y, etc) and for every s. The output could look like this

s  diff  c2  c3
1  w-x   m   -1
1  w-y   m   -2
1  w-z   m   -3
1  x-y   m   -1
etc

I thought the aggregate function should work but I don't know how to define the combinations and pass them to the function argument.

Upvotes: 2

Views: 119

Answers (2)

d.b
d.b

Reputation: 32558

do.call(rbind, lapply(split(dat, dat$s), function(a){
    a$c1 = as.character(a$c1)
    d = setNames(data.frame(t(combn(unique(a$c1), 2, FUN = function(x){
        list(x[1], x[2], a$c3[a$c1 == x[1]] - a$c3[a$c1 == x[2]])
    }))), c("col1", "col2", "val"))
    d$s = a$s[1]
    d$c2 = a$c2[1]
    d
}))
#    col1 col2 val s c2
#1.1    w    x  -1 1  m
#1.2    w    y  -2 1  m
#1.3    w    z  -3 1  m
#1.4    x    y  -1 1  m
#1.5    x    z  -2 1  m
#1.6    y    z  -1 1  m
#2.1    w    x  -1 2  f
#2.2    w    y  -2 2  f
#2.3    w    z  -3 2  f
#2.4    x    y  -1 2  f
#2.5    x    z  -2 2  f
#2.6    y    z  -1 2  f
#3.1    w    x  -1 3  m
#3.2    w    y  -2 3  m
#3.3    w    z  -3 3  m
#3.4    x    y  -1 3  m
#3.5    x    z  -2 3  m
#3.6    y    z  -1 3  m

Upvotes: 1

jmuhlenkamp
jmuhlenkamp

Reputation: 2160

If you are willing to use dplyr something like this should work.

dat <- data.frame(s=c(1,1,1,1,2,2,2,2,3,3,3,3), c1=c("w","x","y","z","w","x","y","z","w","x","y","z"), c2=c("m","m","m","m","f","f","f","f","m","m","m","m"), c3=c(1,2,3,4,5,6,7,8,9,10,11,12))

library(dplyr)
dat$c1 <- as.character(dat$c1)
dat2 <- dat %>%
  left_join(dat, by = c("s", "c2")) %>%
  filter(c1.x > c1.y) %>%
  transmute(s, diff = paste(c1.y, c1.x, sep = "-"), c2, c3 = c3.y - c3.x)

dat2

##    s diff c2 c3
## 1  1  w-x  m -1
## 2  1  w-y  m -2
## 3  1  x-y  m -1
## 4  1  w-z  m -3
## 5  1  x-z  m -2
## 6  1  y-z  m -1
## 7  2  w-x  f -1
## 8  2  w-y  f -2
## 9  2  x-y  f -1
## 10 2  w-z  f -3
## 11 2  x-z  f -2
## 12 2  y-z  f -1
## 13 3  w-x  m -1
## 14 3  w-y  m -2
## 15 3  x-y  m -1
## 16 3  w-z  m -3
## 17 3  x-z  m -2
## 18 3  y-z  m -1

Upvotes: 2

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